1. Field of the Invention.
The invention concerns an applicator which mechanically applies raised pavement markers and, in particular, an apparatus for oriented application of raised pavement markers
2. Description of the Related Art.
Raised pavement markers provide better nighttime and wet delineation of traffic lanes than do painted lines and tapes. Typical raised pavement markers include a retro-reflective surface for orientation toward oncoming vehicular traffic The retro-reflective surface is carried on a marker body, which is adhesively bonded to a roadway surface.
Raised pavement markers are typically bonded to roadway surfaces using one of two alternative adhesives, a two-part epoxy and hot-melt bitumen. A thermal adhesive applicator, Model PD-1001, sold by Pinkley Sales Company of Oklahoma City, Okla., has a roller frame, a heated bitumen reservoir and a dispensing valve. The unit also includes a brake assembly for the wheels. A hand control opens the drip-free dispensing valve to deposit hot-melt bitumen upon a roadway surface.
Considerable development of both retro-reflective material and marker bodies has occurred in recent years One well-known raised pavement marker, a Stimsonite 88 marketed by Amerace Corp. has a truncated pyramid shape. The Stimsonite 88 raised pavement markers may be stacked one upon another. A marker dispenser Model 101 from Downing Manufacturing Company, Tulsa, Okla., is a side-mounted accessory for the bitumen applicator. The dispenser has a four-inch by four-inch vertically mounted tube and a release cam mechanism for dispensing one marker at a time. The Downing dispenser may be effectively used with Stimsonite 88 style markers.
Another particularly desirable raised pavement marker marketed by Minnesota Mining and Manufacturing Company of St. Paul, Minn. (3M), has a rounded upper surface and is described in U.S. Pat. No. 4,875,798 incorporated herein by reference. The 3M raised pavement markers, however, resist attempted stacking because of their rounded upper surface Unfortunately, due to the rounded upper surface of a 3M style raised pavement marker (and the inability to stack 3M raised pavement markers), 3M raised pavement markers cannot be suitably dispensed by a Downing style marker dispenser.
Currently, 3M style raised pavement markers are applied by placing each marker by hand in a roadway deposit of liquid adhesive. Such an application method is slow.
An additional consideration in installing pavement markers is appropriate alignment of the raised pavement markers such that the retro-reflective surface is appropriately illuminated and effectively visible to vehicular traffic. Once the adhesive has "set" readjustment is nearly impossible. A misoriented marker generally must be removed and replaced.
The present invention allows efficient installation of raised pavement markers, such as the 3M style markers referenced above, while eliminating the need to place each marker by hand. Additionally, the present invention provides an improved placement and orientation of a 3M style raised pavement marker on a highway. The present invention has the potential to reduce the cost of installing raised pavement markers.